This project is designed to identify the types of genetic control mechanisms operating during melanogenesis in the fowl. The gene action of five loci based on mutant expression as assayed by high resolution autoradiography will be used as the basis for classification. A control gene locus is defined as any locus which does not produce the molecules characteristic of differentiation, but which affects their expression. Structural mutations would affect the quality of melanogenic molecules, while control gene mutations would affect only their quantity or distribution. Neural crest cell cultures of melanocytes of standard, homozygous mutant, and heterozygotes at the C, Pk, I, Bl, and E coli will be labeled with H3-leucine, as an indicator of newly synthesized melanogenic protein, or with H3-dopa, a melanin substrate. A comparison of results will show how much melanogenesis is going on in each genotype and how well melanogenic proteins bind the H3-dopa. The collated data will be used to construct a model of melanocyte differentiation. Identified control gene mutations will be tested with various inhibitors and compared to standard to determine the roles of cell division, RNA synthesis, and protein synthesis during melanogenesis.